Anna Seniczak

Hydrozetes longisetosus sp. nov. (Acari: Oribatida: Hydrozetidae) – the most primitive European species of Hydrozetes from Poland

The larva, nymphal stages and adult of Hydrozetes longisetosus sp. nov. are described and illustrated, and the relationship of this species with the other European species of Hydrozetes is investigated. This species was first found at the edge of a forest lake, Dury 3, in the Tuchola Forest (Poland). Subsequently, we studied specimens that had been collected in 1976 by Dr H.M. Engelmann 40 km north of Görlitz Niederspree (Germany). Many adults of this species have three setae of the c‐series, which is rare in Hydrozetes and is considered a primitive character. Most adults have two pairs of p‐series setae, which is not common in Brachypylina and is unique among European Hydrozetes. The nymphal stages have many long setae in the marginal part of the gastronotum (whole l‐ and h‐series and seta p 1), and some or all long setae of the c‐ and d‐series, which is unique among European Hydrozetes. In H. longisetosus neotrichy occurs in the h‐series, as in H. parisiensis Grandjean, 1948. Therefore, the former species is closely related to the latter, and also to H. lacustris (Michael, 1882) and H. octosetosus Willmann, 1932, which rarely retain all the c‐series setae in the adults.

The ontogeny of morphological traits in three species of Galumnidae (Acari: Oribatida)

The ontogeny of morphological traits in three members of the oribatid mite family Galumnidae – Acrogalumna longipluma (Berlese, 1904), Allogalumna alamellae (Jacot, 1935) and Galumna alata (Hermann, 1804) – is described and illustrated for the first time and compared with the literature. The juveniles of all species have macrosclerites, microsclerites and a humeral organ, but particular species differ in body size, the length of c-series setae, pattern of integument in anterior part of gastronotum and shape of solenidion ω1 on tarsus I. Their larvae additionally differ by the shape of setae in and dp, presence of transverse furrow on the gastronotum and the length of prodorsal seta in, whereas the nymphs differ by the size of circumgenital macrosclerite and presence of adanal macrosclerite. The adults of these species differ mainly by the presence of lamellar ridge L on the prodorsum and location of seta le, shape of porose area Aa, presence of median pore mp on the notogaster and shape of sensillus. The morphology of juveniles of three species of Pilogalumna Grandjean, 1956 suggests that the presence of transverse furrow in larva and absence of circumgenital macrosclerite in nymphs have probably generic value.

Community Structure of Oribatid and Gamasid Mites (Acari) in Moss-Grass Tundra in Svalbard (Spitsbergen, Norway)

Abstract The mite fauna of patches of High Arctic moss-grass tundra of Svalbard in Petuniabukta, Billefjord (moss, grasses, Salix polaris, bare soil), and adjacent to Vestpynten, Adventfjord (moss, moss mixed with grasses, Cassiope tetragona, S. polaris), were investigated. Our aim was to describe the mite fauna of this tundra with particular focus on the stage structure that is rarely investigated. We observed that the oribatid mites were distinctly more abundant and richer in species (22) than the gamasid mites (7) and their density and diversity varied between vegetation and location. Species diversity of Oribatida and Gamasida and the Shannon H′ index of mite communities were low, and Liochthonius sellnicki or Tectocepheus velatus dominated the Oribatida and Oppiella translamellata and Diapterobates notatus were relatively abundant, while the Gamasida were dominated by Arctoseius multidentatus, with Zercon forsslundi and Z. solenites relatively abundant. The juvenile densities of the Oribatida were usually greater than adults. Eniochthonius minutissimus and Metabelba sp. are new records for Svalbard.

Ontogenetic studies of three species of Gymnodamaeidae (Acari: Oribatida) with a focus on regressions of hysterosomal setae

Ontogeny of loss of gastronotal setae in Arthrodamaeus reticulatus (Berlese, 1910), Gymnodamaeus bicostatus (C.L. Koch, 1836) and Jacotella neonominata Subías, 2004 was investigated. From the larval setation, the protonymph of these species loses three pairs of d-series and two pairs of l-series; these losses continue through subsequent nymphal stages and adult. Between tritonymph and adult, setae of h-series are subject to loss; A. reticulatus loses none, G. bicostatus loses one pair (h 3) and J. neonominata loses two pairs (h 2 and h 3). The nymphs of these species bear the gastronotic exuviae of previous instars, but they differ in the appearance of the exuviae, the manner of their connection with the gastronotum, and the shape of setae c 3 and lp, which in some species helps secure the exuviae to the body. Other aspects of ontogeny of these species are described and illustrated for the first time, and morphological characters that distinguish Arthrodamaeus, Gymnodamaeus and Jacotella are discussed.

Systematic status of Hydrozetes octosetosus Willmann, 1932 (Acari: Oribatida: Hydrozetidae) in the light of ontogenetic and ecological studies

The systematic status of Hydrozetes octosetosus was investigated by comparing this species to H. lacustris, which is the type species for the genus Hydrozetes Berlese, 1902. These species are similar, but probably not synonyms as recently proposed. They differ mainly by the position of notogastral seta lm in the adult and position and length of this seta and total number of long setae in the posterior part of nymphs. In the adult of H. octosetosus, this seta inserts behind the opisthosomal gland opening (gla), but in front of it in H. lacustris. In the nymphs of H. octosetosus seta lm inserts behind gla opening, but medially to it in H. lacustris. In H. octosetosus this seta is very long and the total number of long setae in nymphs is four pairs, while in H. lacustris seta lm is short and the total number of long setae in nymphs is three pairs.

External morphology and ontogeny of three species of Damaeidae (Acari: Oribatida)

The morphology of juvenile stages and ontogeny of Belba compta (Kulczynski, 1902), Epidamaeus bituberculatus (Kulczynski, 1902) and Spatiodamaeus verticillipes (Nicolet, 1855) were described and illustrated for the first time. The juveniles of these species have 12 pairs of gastronotal setae (larva has 12 pairs, protonymph loses d-series setae and gains p-series, and 12 pairs remain in this and other nymphs). They differ mainly by the length of setae c 1 and la in the larva, which are relatively long in E. bituberculatus, short in S. verticillipes and of medium size in B. compta. The nymphs of the latter species have long seta c 3, whereas other species have this seta short. In the nymphs of B. compta, adanal setae are smooth; in E. bituberculatus, these setae have long barbs; but in S. verticillipes, they have short barbs. Ontogeny of leg setae is similar in all species, except for famulus (ϵ), which is emergent in the juveniles of B. compta and sunken in other species; the adults of all species have it emergent. Belba compta and E. bituberculatus lose seta c 3 in the adult, and 11 pairs of notogastral setae remain, whereas S. verticillipes loses seta c 3 and one seta of h-series, which is unique in Damaeidae. The diagnoses of B. compta, E. bituberculatus and S. verticillipes are modified and enriched in the morphological characters of juveniles, and systematic values of some morphological characters of juveniles of Belba von Heyden, 1826, Damaeus CL Koch, 1836, Epidamaeus Bulanova-Zachvatkina, 1957, Kunstidamaeus Miko, 2006, Metabelba Grandjean, 1936, Metabelbella Bulanova-Zachvatkina, 1957 and Spatiodamaeus Bulanova-Zachvatkina, 1967 are discussed.

Setal losses in the dorsal hysterosoma of Plateremaeoidea (Acari: Oribatida) in the light of ontogenetic studies

The Plateremaeoidea demonstrate highly differentiated patterns of dorsal setae on the hysterosoma because these setae are lost in protonymph and adult. Setal loss in protonymph always starts with setae of d-series, and occurs in order, continuing to the l-series and h-series. For example, Aleurodamaeus setosus (Berlese, 1883) and Al. africanus Pletzen, 1963 lose setae of d-series in protonymph, and eight pairs in adult (c-series, l-series, h 2, h 3), so four pairs of setae remain (h 1, p-series). Arthrodamaeus reticulatus (Berlese, 1910), Gymnodamaeus bicostatus (C. L. Koch, 1836) and Jacotella neonominata Subías, 2004 lose also setae la and lm in protonymph, and four pairs (c-series, lp), five pairs (c-series, lp, h 3) and six pairs (c-series, lp, h 2, h 3) in adults, respectively, so six pairs (h-, p-series), five pairs (h 1, h 2, p-series) and four pairs of setae (h 1, p-series) remain, respectively. Licnodamaeus costula Grandjean, 1931 loses additionally seta lp, and Licnobelba latiflabellata (Paoli, 1908) also lose seta h 2 in protonymph, and setae of c-series in adults, so six pairs of setae (h-series, p-series) remain in the former species, and four pairs (h 1, p-series) in the latter species. Morphological characters of juveniles and adults of eight species of Plateremaeoidea are compared.

Morphology of juvenile stages and ontogeny of three species of Damaeidae (Acari: Oribatida)

The morphology of juvenile stages and ontogeny of Belba corynopus (Hermann, 1804), Metabelba parapulverosa Moritz, 1966 and Metabelbella interlamellaris Pérez-Íñigo, 1987 were investigated. The juveniles of these species differ from each other mainly by the shape of seta ex in all juveniles, the presence of seta h 3 and shape of setae c 1, da and dm in the larva, shape of seta p 1 and location of cornicle in the nymphs. Moreover, the larva of B. corynopus carries only humus mass, the nymphs and most adults of this species carry the exuviae of previous instars and humus mass, while the nymphs of other species carry only the exuviae. The formulae of setae on genua and tibiae I–IV of tritonymphs (number of setae on leg segments I–IV) are the same for all these species and those in the literature, but the differences occur on femora I–IV and trochanters III and IV. The setal formula of femora I–IV clearly separates Belba von Heyden, 1826 from Metabelba Grandjean, 1936 and Metabelbella Bulanova-Zachvatkina, 1957, whereas the formula of trochanters III and IV separates Belba from Metabelbella. The differences in the number of setae on these leg segments between Metabelba and Metabelbella are indistinct. In contrast, the setal formula of tibiae I–IV in the adults is specific for each genus (4-5-3/4-4 in Belba, 4-5-5-4 in Metabelba and 4-4-4-4 in Metabelbella), has generic value and is consistent with Miko (2006. Damaeidae. In: Weigmann G., editor. Hornmilben (Oribatida) [Oribatid mites (Oribatida)]. Keltern (Germany): Goecke & Evers; p. 179–207. (Die Tierwelt Deutschlands [The fauna of Germany]; part 76. Dahl, F, series founder). whereas the formula of femora I–IV separates Belba from Metabelba and Metabelbella, and formula of trochanters III and IV separates Belba from Metabelbella, as in the tritonymphs.

Fine structure of the gnathosoma of Archegozetes longisetus Aoki (Acari: Oribatida, Trhypochthoniidae)

Oribatida are one of the main groups of Acari comprising mostly important decomposers in soils. Most species are particle feeders, an exceptional mode of nutrition in Arachnida. Hence, their feeding organs, the gnathosoma, are of special functional interest. We studied nearly all components using scanning and transmission electron microscopies as well as reconstructions based on synchrotron X‐ray microtomography from the model oribatid Archegozetes longisetosus. Besides cuticular structures, we describe the full set of muscles and confirm the presence of a trochanter remnant at the base of the chelicera. Setae on the prodorsum and the anterior and posterior infracapitular setae are mechanoreceptors innervated by two dendrites ending with tubular bodies. Dendrites of adoral setae, anterior setae of the chelicerae, and the supracoxal setae show neither obvious tubular bodies nor wall or terminal pores. Thus their function remains obscure. For the first time, a muscular proprioreceptor has been found in Arachnida. It likely monitors the actions of muscles moving the movable digit of the chelicera. Glandular structures within and associated with the gnathosoma are described. Dermal glands represented by secretory porose areas are found within the infracapitulum. More complex associated glands comprise the podocephalic glands and the infracapitular glands, the ducts of which were traced completely for the first time. The components described are mostly fundamental for the gnathosoma of Actinotrichida (Acariformes), one of the two lineages of Acari, to which Oribatida belong. The gnathosoma is generally considered the most relevant putative synapomorphy of Acari. Since the monophyly of Acari has become more and more questionable during the last decades, a thorough reinvestigation of this body part is necessary for a comprehensive understanding of acarine and even arachnid phylogeny and evolution. This article provides a starting point of such a re‐evaluation of the gnathosoma. J. Morphol. 2011.

Microarthropod communities of industrially disturbed or imported soils in the High Arctic; the abandoned coal mining town of Pyramiden, Svalbard

The terrestrial environment of the High Arctic consists of a mosaic of habitat types, both natural and anthropogenic. At the abandoned coal mining town of Pyramiden, Svalbard, topsoil was imported from southern European Russia. This, and further industrial disturbance in the town, offers new opportunities for the native invertebrate fauna, but may also introduce alien, potentially invasive, species. Few studies have examined anthropogenic habitats in the High Arctic. But increasing activity, including industry and tourism, requires an understanding of the responses of the Arctic to such pressures. The microarthropod communities observed in the settlement were substantially different from the natural tundra. In the settlement, nine species of mesostigmatid mite occurred (three new records for Svalbard; Dendrolaelaps foveolatus) and two additional not identified to species (Halolaelaps sp., Arctoseius sp.), 26 species of Collembola (12 not seen in the natural tundra close to Pyramiden) and two new records (Thalassaphorura debilis and Desoria tigrina), but only five Oribatida. This is set against 8, 20 and 24 species respectively for Mesostigmata, Oribatida and Collembola from natural tundra in the vicinity. The imported soils remain to be yet fully exploited by the native microarthropod fauna. Taxa disparities may result from differential mortality during collection and shipping of the soil, and subsequent colonisation. While none of the introduced species appear to be invasive, responses to climate change scenarios are difficult to project. Understanding of alien species and the timespans required for colonization by native faunas are of importance for remediation and reclamation projects in polar regions.